Acceptable Operator Exposure Level risk assessment

The risk characterization procedure will result in a quantitative comparison per substance of the outcome of the exposure assessment and of the effects assessment. This comparison is made through the ratio PEC/PNEC. The generic name for PEC/ PNEC in EUSES is risk characterization ratio (RCR). Other ratios are used in EUSES for the risk characterization such as the margin of safety (MOS) or the ratio of the estimated no-effect or effect level parameter to the estimated exposure level for human subpopulations and the acceptable operator exposure level (AOEL). 

The risk assessment comprises an effect assessment (hazard identification and hazard characterization) and an exposure assessment. The principles for the effect assessment of the active substances are in principle similar to those for existing and new chemicals and are addressed in detail in Chapter 4. Based on the outcome of the effect assessment, an Acceptable Daily Intake (ADI) and an Acceptable Operator Exposure Level (AOEL) are derived, usually from the NOAEL by applying an overall assessment factor addressing differences between experimental effect assessment data (usually from animal studies) and the real human exposure situation, taking into account variability and uncertainty for further details the reader is referred to Chapter 5. As a part of the effect assessment, classification and labeling of the active substance according to the criteria laid down in Directive 67/548/EEC (EEC 1967) is also addressed (Section 2.4.1.8). 

Exposure estimates that are required for risk assessment may be obtained from chemical-specific field studies, or from extrapolations from other field studies. This requires high-quality exposure data that have been obtained under conditions relevant for the exposure and use scenarios under consideration (Krieger et al, 1992 Eenske and Teschke, 1995 Krieger, 1995 Turnbull et al, 1995). For risk assessment purposes, the exposure data obtained for relevant use scenarios can be compared with an appropriate accepted exposure level (e.g. Acceptable Operator Exposure Level (AOEL)) based on the toxicological profile of the compound. 

Figure 5.1 Tiered data requirements for estimating operator exposure for use in risk assessment and regulation of pesticides (AOEL, acceptable operator exposure level)...

In order to assess risk to individuals following dermal exposure to a pesticide, dermal absorption data are often required to convert dermal deposition data to estimates of systemic exposure. These estimates of systemic exposure are then compared with the No Observed Adverse Effect Levels (NOAELs) from oral toxicity studies or limit values (for instance. Acceptable Operator Exposure Levels (AOELs)) derived from these oral data (Bos et at., 1998 Rennen et al 1999). As noted in the introduction, oral studies are generally used because the toxicology database is typically focused on the oral route of exposure. 

Rennen, M.A.J., LA. van de Gevel, C. de Heer and B.C. Hakkert (1999). Occupational Risk Assessment of Pesticides Method Used in the Netherlands for the Setting of Acceptable Operator Exposure Levels for Active Substances, TNO Report V99.324, TNO Nutrition and Food Research Institute, Zeist, The Netherlands. 

From these considerations, the most appropriate No Observed (Adverse) Effect Level (NO(A)EL) is chosen for the risk assessment. From this NO(A)EL the Margin of Safety (MOS) or Acceptable Operator Exposure Level (AOEL) is derived by the incorporation of safety factors. The safety factor used depends on the type of study used to derive the endpoint and the severity of the effect. 

What-lf Hazard Analysis. This hazard assessment method utilizes a series of questions focused on equipment, processes, materials, and operator capabilities and limitations, including possible operator failures, to determine that the system is designed to a level of acceptable risk. Users of the What-If method would identify possible unwanted energy releases or exposures to hazardous environments. Bulletin 135 contains procedures for use of a What-If checklist. For some hazards, a What-If checklist will be inadequate and other hazard analysis methods may be used. 

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